FAILED: patch "[PATCH] ksmbd: smbd: fix dma_unmap_sg() nents" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 98e3e2b561bc88f4dd218d1c05890672874692f6
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026012757-wrench-plated-2f22@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 98e3e2b561bc88f4dd218d1c05890672874692f6 Mon Sep 17 00:00:00 2001
From: Thomas Fourier <fourier.thomas@gmail.com>
Date: Fri, 9 Jan 2026 11:38:39 +0100
Subject: [PATCH] ksmbd: smbd: fix dma_unmap_sg() nents

The dma_unmap_sg() functions should be called with the same nents as the
dma_map_sg(), not the value the map function returned.

Fixes: 0626e6641f6b ("cifsd: add server handler for central processing and tranport layers")
Cc: <stable@vger.kernel.org>
Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/server/transport_rdma.c b/fs/smb/server/transport_rdma.c
index f585359684d4..8620690aa2ec 100644
--- a/fs/smb/server/transport_rdma.c
+++ b/fs/smb/server/transport_rdma.c
@@ -1353,14 +1353,12 @@ static int get_sg_list(void *buf, int size, struct scatterlist *sg_list, int nen
 
 static int get_mapped_sg_list(struct ib_device *device, void *buf, int size,
 			      struct scatterlist *sg_list, int nentries,
-			      enum dma_data_direction dir)
+			      enum dma_data_direction dir, int *npages)
 {
-	int npages;
-
-	npages = get_sg_list(buf, size, sg_list, nentries);
-	if (npages < 0)
+	*npages = get_sg_list(buf, size, sg_list, nentries);
+	if (*npages < 0)
 		return -EINVAL;
-	return ib_dma_map_sg(device, sg_list, npages, dir);
+	return ib_dma_map_sg(device, sg_list, *npages, dir);
 }
 
 static int post_sendmsg(struct smbdirect_socket *sc,
@@ -1431,12 +1429,13 @@ static int smb_direct_post_send_data(struct smbdirect_socket *sc,
 	for (i = 0; i < niov; i++) {
 		struct ib_sge *sge;
 		int sg_cnt;
+		int npages;
 
 		sg_init_table(sg, SMBDIRECT_SEND_IO_MAX_SGE - 1);
 		sg_cnt = get_mapped_sg_list(sc->ib.dev,
 					    iov[i].iov_base, iov[i].iov_len,
 					    sg, SMBDIRECT_SEND_IO_MAX_SGE - 1,
-					    DMA_TO_DEVICE);
+					    DMA_TO_DEVICE, &npages);
 		if (sg_cnt <= 0) {
 			pr_err("failed to map buffer\n");
 			ret = -ENOMEM;
@@ -1444,7 +1443,7 @@ static int smb_direct_post_send_data(struct smbdirect_socket *sc,
 		} else if (sg_cnt + msg->num_sge > SMBDIRECT_SEND_IO_MAX_SGE) {
 			pr_err("buffer not fitted into sges\n");
 			ret = -E2BIG;
-			ib_dma_unmap_sg(sc->ib.dev, sg, sg_cnt,
+			ib_dma_unmap_sg(sc->ib.dev, sg, npages,
 					DMA_TO_DEVICE);
 			goto err;
 		}